G1800 starting circuit problems?

[Delem2830]

I have an old G1800. It has been running well. Recently it won't start. It cranks over slowly and the cranking won't stop until the battery cables are disconnected.
The first time it happened, I couldn't get it disconnected fast enough and it melted a couple ground wires. I then replaced the wires and it started up fine. Then, on the next day, it wouldn't start again (same problem: slow cranking and cranking continued until the battery cables were disconnected).

I have bench tested the solenoid and starter and they operate well at the bench. Prior to this problem, the ignition switch, stop solenoid, start solenoid and fuel pump had all been replaced recently. I have also now replaced the battery leads and tested the battery, all are good. And have tested for shorts using a test light.

So far, I am not finding the issue. I would rather not spend $170 plus tax on a new Combination Box, but need some other ideas to try.

Thanks for any suggestions or answers.

 

[Dave_eng]

Have you made any changes to the tractor. The fact that ground wires melted is a big clue that something in the wiring is wrong. Which ground wires are you referring to?

The ground battery cable should tolerate the starter running continuously. If other ground wires are frying perhaps your main ground cable is defective, or not making clean solid contact with the engine and other ground wires are having to take loads they were never designed for.

Also, a poor engine ground would limit or prevent the glow plugs from working and thus the engine not starting.

Next I think you need to focus on the small wire on the starter solenoid as it is the one to engage the solenoid.

If the engine continues to crank and there is no power on that wire then your problem is in the starter no matter what your bench tests indicate.

If power continues to flow to that small wire, then you have to work backwards.

If you have a wiring diagram in an owner's manual post it plse.

I looked in Kubotabooks at a G6200 which tractor data said was the model after your G1800.

The wiring is simple with only two safety switches in the circuit between the key and the starter solenoid. These safety switches can only prevent the starter from engaging not power the starter themselves.

There is no relay between the key switch and the starter solenoid.

Do you have a test light? Less than $10.

With a test light, remove the small wire on the starter solenoid, connect the test light alligator clip to the end of the wire and put the sharp end of the light to any ground point. Keep trying the key to the start position and then release. The test light should go on and then off as soon as the key is released.

This test is important. It also avoids having the starter continue to run until you get a battery cable off.

Once you have done the above test and have the results we can focus in on what your problem may be but I strongly suspect ground problems will be your
cause. Remove the ground cable from the engine or frame of the tractor completely and clean the metal until it is shiny.


Dave

 

[Delem2830]

Thanks Dave.
Here's the wiring diagram, attached. I hope it's legible.
I will try the solenoid/test light and see what happens.

The ground wires that burned were front the stop solenoid and a single wire running between a main bundle and that attached to the same lug on the frame as the negative battery terminal. I replaced all of the burned wires.

 

[Delem2830]

Dave,
Just tested the solenoid signal wire with the test light. I grounded the light probe to the ground wire that connects directly to the stop solenoid (the only obvious ground spot I could reach while sitting on the seat to engage all the safety switches). The light turned on and off in sync with the ignition key being in "run" or "off". This ground wire connects through the same frame lug and that connects the negative battery cable to the battery ground. The main battery connection to the frame is clean and all the ground wire eyelets that connect to the frame at this point are new also.

Is it possible that the the ground path from the starter (that goes through the frame components) to the battery ground is not conducting??? Can a simple jumper wire be a possible solution?

Thanks again. Don

 

[Dave_eng]

Dave,
Just tested the solenoid signal wire with the test light. I grounded the light probe to the ground wire that connects directly to the stop solenoid (the only obvious ground spot I could reach while sitting on the seat to engage all the safety switches). The light turned on and off in sync with the ignition key being in "run" or "off". This ground wire connects through the same frame lug and that connects the negative battery cable to the battery ground. The main battery connection to the frame is clean and all the ground wire eyelets that connect to the frame at this point are new also.

Is it possible that the the ground path from the starter (that goes through the frame components) to the battery ground is not conducting??? Can a simple jumper wire be a possible solution?

Thanks again. Don

Buy a starter grade or sized wire with eyes on both ends. Connect one end to a starter mounting bolt after polishing it up and the other end to the frame lug.

This sure looks like the solution. The starter relies on metal to metal contact with the engine block for its ground. Rust between the starter and engine block can make the ground circuit not good enough to sustain high amperage loads while starting. Also the electrical connection between the engine block and the tractor frame is critical. Now the power your are sending through the starter is looking for other ways back to the battery and in doing so is melting small ground wires such as the engine stop solenoid.

Dave

 

[D2Cat]

Yep, what Dave said.

Often times just remove the starter and clean the face of the starter where it bolts to the flywheel, and the flywheel surface. Then you're good for many more years!

 

[Delem2830]

Update:
I installed a ground wire from starter to main ground on the frame as suggested. I also removed the starter and cleaned everything down to the shiny, bare metal. Then tried it again but unfortunately, the same problem persists: the starter runs enough to turn the engine over slowly, but when the ignition key is released or shut off, the starter continues to run until the battery ground is disconnected.

New observation: After this happens, and after the battery is disconnected; when I again touch the disconnected battery lead to the negative post on the battery, there is a loud click, maybe from the starter gear area(?) and after that one click, the battery lead can be reconnected to the post and the click sound doesn't happen any more.

I'll check the voltage drop across the starter. But even if the Voltage measurement is indicating that the starter is failing, why would it keep running (after the switch is off and until the battery is disconnected)?
Thanks again.

 

[Dave_eng]

Update:
I installed a ground wire from starter to main ground on the frame as suggested. I also removed the starter and cleaned everything down to the shiny, bare metal. Then tried it again but unfortunately, the same problem persists: the starter runs enough to turn the engine over slowly, but when the ignition key is released or shut off, the starter continues to run until the battery ground is disconnected.

New observation: After this happens, and after the battery is disconnected; when I again touch the disconnected battery lead to the negative post on the battery, there is a loud click, maybe from the starter gear area(?) and after that one click, the battery lead can be reconnected to the post and the click sound doesn't happen any more.

I'll check the voltage drop across the starter. But even if the Voltage measurement is indicating that the starter is failing, why would it keep running (after the switch is off and until the battery is disconnected)?
Thanks again.

Thanks for following the path suggested. I am sorry you still have a problem but think the things you have done will prove to be part of the solution to melting ground wires.

Starter solenoids have a circuit within themselves that is not widely known.
The solenoid actually consists of two coils of wire, one within the other.
There is a coil of wire with high current flow to pull the gear into engagement with the flywheel. There is a second coil of wire within the solenoid whose job it is to hold the starter in engagement. The movement of the solenoid plunger trips a contact and turns off the high current pull in coil so as to not overheat the solenoid.

I suspect something is amiss within the solenoid and the hold in coil is remaining energized after you release the key.

I would suggest taking your starter to a local starter and alternator repair shop. They will have a solenoid to replace your defective one. Alternatively, you may decide to buy a new starter.

Dave

 

[ddp69camaro]

Hi Delem2830, Did you ever figure out what was causing your starting issue? I'm having a very similar issue, except I'm not getting ground wires melting. I have the Workshop Manual, so I've been testing circuits and components, but everything so far has checked out good (ignition switch, starter, starter solenoid, wiring harness, PTO safety switch, ground connections). Any help would be appreciated.